Process for producing uranium halides



' Oct. 29, 1957 E. v. MURPHRE'E 2,811,414

' PRocEs's'FoR PRODUCING URANIUM HALIDES Filed April 9, 1942 2 Sheets-Sheet 1 J JEFARATO? 6 6 I .s'roznce 3 Among! CONVEYOR "A C ran scar/BEER III-2::-

Dos-r f t SEPA RATOR REACTOR INERT COOLER OoLER W 2 \I I 25 53 Oct. 29, 1957 E. v. MURPHREE 2,811,414

PROCESS FOR PRODUCING URANIUM HALIDES Filed April 9, 1942 2 Sheets-Sheet 2 W WN N rnocnss non PRODUCING URANIUM HALIDES Eger V. Murphree, Summit, N. J., assignor, by mesne assignments, to the United States of America as represented by the United States Atomic Energy Commission Application April 9, 1M2, Serial No. 438,284 18 Claims. (Cl. 24.3-14.5)

The present invention relates to the art of refining uranium bearing ores and to segregating purified uranium compounds therefrom, and to a process for manufacturing higher halides of uranium and equivalent metals, especially fluorides. The invention will be fully understood from the following description and the drawings.

Fig. 1 of the drawing is a diagrammatic view in sectional elevation of an apparatus for carrying out a process in a batch or semi-continuous manner, and

Fig. 2 is a similar view of a fully continuous apparatus showing the paths of flow of the various materials.

One object of the present invention is to devise a convenient, cheap and efiicient method for refining ores containing compounds of metals such as uranium, tungsten, molybdenum and vanadium. Another object is to provide a method for producing uranium and tungsten compounds of a high degree of purity, and a third object is to produce higher halides, especially fluorides of such metals. Other objects will be apparent to those skilled in the art.

Referring to the drawing, especially Fig. l, the uranium bearing ore or other raw material which is in the form of a higher oxide, such as uranosic'oxide, U308, is conveyed from hopper 1 by a screw conveyor 2 into a storage bin 3. The oxide is in a finely divided form, for example at least 50 mesh or finer, and is collected in thevessel 3, which is an elevated bin with closed top constructed of iron or steel. At its lower end the vessel is provided with a feed pipe 4 from which the finely divided material can be withdrawn as a fluidized stream. Bythis term is meant that the powder is maintained in a free flowing condition which is accomplished by blowing into the bin a relatively small amount of a gas by pipe 5. This fluidized state may be considered as a state of suspension of the solid in the gas but the suspension is a very dense one which in appearance closely resembles a liquid in that it flows readily and exerts static and dynamic heads just as is the case with a liquid. In the upper portion of vessel 3, cyclone or dust'separating devices are diagrammatically shown at 6 and are provided to separate the bulk of the powdered solid from thegas which is allowed to escape through a pipe 7. This gas may contain some solid and it may be recovered separately, but as indicated and as will be described later, it is preferable to recover it along with the solid from other gas streams. It will be understood that the chamber 3 may be used tofeed a plurality of different batch reactors of which, however, only one indicated by numeral 8 is shown in the drawing. This is a tall, vertical chamber, constructed or lined with copper, nickel or alloys thereof, such as Monel metal, which are capable of withstanding the highly corrosive action of free hydrogen and hydrogen halides at elevated temperatures.

The fluidized powder flows from the vessel 3 through a standpipe 4 which connects at its lower end with a pipe 4b through which the flowing powder is conveyed to a heat exchanger 9 and thus into the lower portion of the reaction chamber 8. When suflicient powder has been transferred into the chamber 8, valve 4a in the lower part of the standpipe is closed or the streamtmay be diverted to some other reactor similar to 8, but not tate Patent 10 shown. It will be observed that no pump is provided for forcing the fluidized stream from the bin 3 into the reactor 8 and no such pump is necessary because of the elevated position of the feed bin 3, and the fluidized stream will pass rapidly down the column 4 and into the reactor under the influence of the static head. It is desirable to add small amounts of gas to the standpipe in order to insure the maintenance of this fluidized condition throughout the stream. Such gas may be an inert gas, nitrogen or flue gas, but hydrogen may also be employed and indeed is frequently preferred in view of the fact that this gas is employed as one of the reactants in the reaction zone.

Hydrogen is supplied by a pipe 10 and hydrogen fluoride by pipe 11 and these gases together with the inert gas from pipe 12 are fed through control valves into a manifold 13. From the manifold the gases alone or in admixture, as will be explained below, are then passed into the pipe 13a and thence through the exchanger 9 into reaction chamber 8.

In the upper portion of the reaction chamber 8, or if desired in a separate housing, cyclone or dust separators which are shown diagrammatically at 14 are provided so as to return the bulk of the solid carried by the gas to the reaction chamber, and the gas itseif, which may of course still contain small amounts of dust, finds exit by a pipe 14 and then passes through a more complete powder removing apparatus shown at 15. The apparatus shown at 15 is an electrostatic or Cottrell precipitator unit, although other types of separators may be employed. The precipitated solid is returned to the reaction chamber by a pipe 15a while the gas flows overhead by a pipe 16 through an absorber 17, scrubber 18 and dryer 19, and thence by a pump 2%? and a line 21 back to the pipe 4b mentioned before, and is thus free to flow up through the exchanger again and return to the reactor. 1

The dryer and the absorber may, of course, be utilized or they may be by-passed. The purpose of theabsorber is to remove HF from the gas as will be explained and for this purpose solid alkali fluorides can be used. The HF can then be recovered by heating the absorbent. The scrubber washes the gases with water or soda to remove silicon fluoride and fluorides of other metalloids if present and the purpose of the dryer is to remove the water. Any solid or liquid dehydrating agents may be used, but if desired, mechanical apparatus for separating water can be substituted.

The reactor 8 may be operated in a number of different ways. In the first place, if desired, hydrogen alone or hydrogen with inert gas is fed to the reactor 8 and circulated therethru for a period of several hours, during which the uranosic oxide is reduced to uranous oxide, U02. This reaction can be carried out at temperatures in the range from 400 to 900 C., preferably at about 600 C.

The reaction is exothermic and the heat exchanger 9 may be used only for the purpose of heating the powder to the reaction temperature when it is first introduced. However, in relatively small apparatus where heat losses are abnormally high, it may be necessary to continue supplying heat through the exchanger 9 in order to maintain temperature even in spite of the exothermic character of the reaction. In large apparatus, however, once the equipment has been raised to the proper temperature, it should maintain itself and heat may be abstracted from the gases by means of the heat exchanger 9 and in this way the reactor is held at proper temperature. A preferable method of holding the temperature, however, is to provide a withdrawal pipe, denoted by 22, from the lower partof reaction chamber 8 and a flowing pipe 23 through the exchanger 9 and thus returned to the reactor. The higher heat capacity of the recirculated solid makes it a better medium for controlling temperature than the recirculated gas stream.

Aftera suitable period of time has elapsed anduranosic oxide is substantially completely reduced, the hydrogen gas may be replaced in whole or inpart by anhydrous hydrofluoric acid gas from the pipe 11 mentioned before and the circulation is continued for another period of time in which the hydrofluoric acid gas is recirculated through the same system as indicated before for the hydrogen. The reaction thus induced is again exothermic and the uranous oxide is converted to uranium tetrafluoride, UF4, at temperature of 400 to 700 C. It Will be understood that in the course of both of these steps, the solid material, whether in the form of uranosic oxide, uranous oxide or uranium tetrafluoride, is maintained throughout in a fluidized state and circulates freely just as a liquid through the circulating pipes.

Instead of the above mentioned method in which separate stages of reduction with hydrogen and conversion with hydrogen fluoride are performed separately, it has been found that both reactions may be carried out simultaneously with a mixture of hydrofluoric acid gas and hydrogen. Both reactions may be carried out at substantially the same temperature, from 400 to 700 C., preferably at about 500 C., and in this manner both reactions may be conducted at one and the same time.

Experience has shown that the stepwise method of using hydrogen and hydrogen fluoride separately and in turn is preferable to the method just disclosed since higher yields are obtained in the previous manner and objectionable by-products are avoided.

After the material in reaction chamber 8 has been converted substantially completely to uranium tetrafluoride, it is withdrawn through pipe 22 from the reactor and passed by a pipe 24 through a cooler 24a. Fluorine gas may be added through pipe 25 and after mixing with the cooled fluidized stream of uranium tetrafluoride, it passes through a short reactor which may be in the form of a coil of pipe shown at 26 which is maintained at 200 to 400 C., preferably about 300 C. The reaction which occurs is the conversion of the tetrafluoride into uranium hexafluoride, UFs. This reaction is quite rapid at the temperatures disclosed and the product produced is sufliciently low boiling so that it is vaporized immediately on formation. The mixture of vapor with such solid as is unconverted, impurities and the like is discharged into the dust separator 27. The solid material drops out and is removed by pipe 28 while the vaporous hexafluoride and gas pass over by means of a pipe 29 through a cooler 30 and into a collection drum 31. While the hexafluoride is solidified, the residual gas is pulled off through pipe 32 and thereafter the hexafluoride of uranium is liquefied under pressure and drawn off at 33. If it should be desired to produce uranium tetrafluoride, it will be understood that the fluorine gas added by pipe 25 may be omitted and the uranium tetrafluoride will then be collected as a solid, the fluid stream containing it being transferred to separator 27 by a by-pass line 27a.

The apparatus or process disclosed heretofore has been batch or semi-continuous, but it may be made fully continuous and such an apparatus is shown in Fig. 2. In this drawing a freight car 60 is shown from which the uranosic oxide in finely divided form is removed by a suction conveyor 61 which discharges into a bag filter 62. The exhausted gas passes out through a pump 63 and the separated solid falls into a feed bin 64. This bin is similar to the one shown in the prior drawing and the material therein is put into a fluidized state by the introduction of a carrier gas through pipe 65, such as in the manner described above. At the upper end of the bin dust collecting apparatus shown diagrammatically at 66 is provided and the gas escaping from the top is taken off by pipe 67. From the bottom of the feed bin a standpipe 68 is provided through which the fluidized material flows through a heat exchanger coil 70 and into a reaction chamber 71. Hydrogen gas may be supplied by a pipe 69 which also discharges into pipe 68 mentioned above.

The reaction chamber 71 is similar to the one disclosed heretofore with the dust collector 73 at the upper end and pipe 74 for taking off the gas. The gas then passes through a Cottrell precipitator 75 and the separated solid is returned to the reactor by pipe 75a. The gas passes from the precipitator by pipe 76 to an absorber '78, scrubber 79, dryer 79a, as in the apparatus first described, and thence by pipe 80 for recirculation to the reactor. The lower part of the reactor may be provided with two conical collectors and one of these is provided with a pipe 72 so that a portion of the fluidized contents of the reactor may be drawn 0E and recirculated through coil 70 for heat control purposes. The second conical collector feeds a pipe 81 through which another portion of the solid which has now been reduced to uranous oxide is passed to the second reaction step. If desired, inert gas may be added to the reactor so as to strip the hydrogen out of the fluidized solid flowing through the pipe 81 and this is accomplished by pipe 81a, but this is not required since the presence of hydrogen is not objectionable in the subsequent treatment.

Hydrogen fluoride is added through a pipe 32 mixing with the flowing stream in pipe 81 and thence through a heat exchanger 83 and into a second reactor 84. This reactor is quite similar to 71 in a design with the dust collectors 86, the Cottrell precipitator 88, air absorber 89, scrubber 90. The final gas flows out through a pump 92. A portion of the contents of this reactor, which will be understood to be in fluidized state, is collected and recirculated by means of the pipe 85, while a second portion of the material, which is largely in the form of uranium tetrafluoride, is taken from the second conical collector and passed through the cooler 96. This stream is stripped of hydrogen fluoride by the introduction of inert gas at 9611 and the remaining fluidized stream is then mixed with gaseous fluorine from pipe 97 and in passing through the reactor 98 the solid is converted into hexafluoride. It will be recalled that the uranium hexafluoride will be vaporized substantially as it is formed in the short reactor 98 and the solid impurities will be separated by the cyclone separator 99. Vapors pass overhead by pipe 100 through a refrigerated cooler 101 and into the collector 102 in a solid condition. Residual gas is taken off at pipe 103 while the uranium hexafluoride is removed as a liquid by pipe 104. The gas stream from pipe 103 may be recirculated or the fluorine may be otherwise recovered.

As above mentioned, the operation of this apparatus is fully continuous and it will be understood that the reactor 71 is used solely for the purpose of reducing the uranosic oxide to uranous oxide, while reactor 84 is operated solely for the purpose of converting the uranous oxide to uranium tetrafluoride. As has been disclosed in connection with the batch apparatus first described, these two reactions may be carried out simultaneously, although it is preferable to separate them as disclosed above, and this is also true in connection with the continuous system. In such case, hydrogen fluoride from pipe 82 will be mixed with hydrogen from pipe 69 by means of the valved pipe 94 and thus a mixture of uranosic oxide, hydrogen and hydrogen fluoride will be passed simultaneously into the two reactors 71 and 84, employing the bypass line 93 for feeding the second reactor and a pipe 96b for passing the product from the first reactor 71 into the cooler 96 for the final conversion to hexafluoride. It is also preferred to employ a bypass line so that the gaseous materials from the two reactors will be mixed and circulated through a single system back to the two reactors. It will be observed in this case that the two reactors 71 and 84 are operating in parallel. If desired, only a single reactor need.

be used.

In the continuous system there are considerable advantages over the batch system. Control is more accurate and the operation would be cheaper, especially in treating large quantities. The reaction temperatures and other conditions are substantially the same as in the batch operation, the first two reactions occurring at temperatures from 400 to 700 0., preferably about 500 C., and the final reaction at temperatures from 200 to 400 C., preferably about 300 C. The times required for these reactions vary with the conditions and the partial pressure of the reactive gases. In general, the time will be from a few minutes to several hours. The exact time can best be determined by experience and by the withdrawal at intervals of samples and the analysis thereof. It will be understood further that by employing the solid materials in a fluidized state, as explained above, it is possible to cause the solids to flow like liquids into and out of the two reactors whether in series or in parallel. In order to induce a flow, that is to say to put the material into a fluidized condition, it is necessary to employ at least .005 to .025 cubic feet of gas for each pound of the solid, and it will be understood that the apparent density of the fluidized material depends largely upon its content of solid material. It will be understood that the minimal quantity of gas indicated above is necessary to cause the flow through the apparatus, but that larger quantities of gas may be added if desired. It will be understood that the upward velocity of flow of gas in the reactors is of considerable importance such as to prevent the dropping out of the major portion of the solid in the bottom of the reactor, but in any case it allows suflicient slippage between the gas and solid so that the time of residence of the solid in the reactor is greater than that of gas. It will be clear that the physical condition of the solid in the reactors will simulate a boiling liquid, the gas continuously being passed up through the mass of dry finely divided particulate material whereby a major portion of the particles are maintained in fluid suspension. An intimate contact between the solid and gas' is thereby provided. Thus, the velocity of flow in each of the reactors is preferably within the range from .10 to 10.0 cubic feet of fluidized mixture per second. The ratio of the solid to the gas is subject to considerable variation, but is within the range of about 1 to 30 pounds of the solid per cubic foot of gas, preferably at about 15 pounds per cubic foot of gas. That is to say, the ratios given above indicate the contents of the reactor. It will be obvious that the amount of hydrogen or hydrogen fluoride must be ultimately suflicient for the reaction contemplated and for practical purposes an excess is always employed. The purpose of the additional gas is to decrease the apparent density of the fluidized mixture. Flow is then induced from one portion of the apparatus to another by providing a sufficient drop in the static head between the two portions of the apparatus, and the dif-' ference in head between any two portions of the apparatus, as will be understood, is measured by the difference in the product of the two densities of the opposing column by their corresponding height. By carefully designing the apparatus in this manner, a flow can be produced throughout the entire apparatus including the circulation lines without the necessity of any pump operating on a solid-containing fluid.

While the above description deals with uranium hearing materials, it will be understood that tungsten compounds may be treated in the same manner. The process also applies to vanadium and molybdenum compounds which will be converted to volatile fluorides in the same manner. If it is found desirable to separate the mixtures of volatile fluorides, that is to say if the original material contains mixtures of uranium, molybdenum, vanadium and tungsten, it will be found that they may be separated best by fractional distillation, using conventional packed or plate columns of suitable metals. Other methods such as fractional crystallization and the like may be employed.

In refining ores, the common impurities present are alkali and alkaline earths, as oxides, sulfides, carbonates, silicates and the like, and metals such as aluminum, copper, manganese, lead, iron, nickel, cobalt and metalloids such as silica mentioned above, arsenic and antimony. During the refining process the alkaline oxides and earth oxides will, of course, be converted to fluorides. Together with the metal fluorides, these are separated from the dust collector 27 in Fig. l and 99 in Fig. 2, since the fluorides of these materials are not volatile at the temperature involved, as is the case with uranium and its equivalents. The metalloids are similarly converted to fluorides in the hydrogen fluoride treatment and will go overhead with the gas from the reactors. These materials may be removed with water or with caustic soda, as indicated in the washing step shown in the drawings.

The present process is particularly advantageous as a method for producing highly purified uranium compounds and the compounds of its equivalents and if desired the product of the usual wet chemical methods now employed for refining these materials may be finally purified by the present method which will thus produce compounds of the desired metals in a high degree of purity.

The present invention is not to be limited by any theory of the operation of the apparatus or the particular reactions occurring in the separate vessels nor to the production of any particular halide, but only by the following claims in which it is desired to claim all novelty inherent in the invention.

I claim:

1. In a process for producing a uranium tetrahalide from an oxide of uranium, the step of passing a gas containing a hydrogen halide into a substantially dry mass of finely divided uranium dioxide particles at a velocity sufficient to maintain a major portion of the particles in fluid suspension and under conditions to convert the uranium dioxide to the uranium tetrahalide.

2. The process recited in claim 1 wherein the hydrogen halide is hydrogen fluoride.

3. In a process for producing a uranium tetrahalide from an oxide of uranium higher than the dioxide, the steps of passing hydrogen and a hydrogen halide in the gaseous state into a substantially dry mass of finely divided particles of the higher oxide of uranium at a velocity suflicient to maintain a major portion of the particles in fluid suspension and under conditions to convert the higher uranium oxide to uranium dioxide and then to the uranium tetrahalide. I i

4. The process recited in claim 3 wherein the higher oxide of uranium is uranosic oxide and the hydrogen halide is hydrogen fluoride.

5. The process recited in claim 3 wherein the hydrogen and the hydrogen halide are simultaneously passed into the mass of particles.

6. The process recited in claim 3 wherein the hydrogen and the hydrogen halide are successively passed into the mass of particles.

7. In a process of preparing a uranium fluoride from an oxide of uranium, the steps of passing a gas containing hydrogen fluoride into a reaction zone containing a substantially dry mass of finely divided uranium dioxide particles at a velocity sutficient to maintain at least a major portion of the particles in fluid suspension and under conditions to convert the uranium dioxide particles to uranium tetrafluoride particles, withdrawing the uranium tetrafluoride particles from the reaction zone, and contacting said particles with a gas containing fluorine under conditions to form uranium hexafluoride.

8. A process of preparing uranium hexafluoride which comprises passing a gas containing hydrogen fluoride into a reaction zone containing a substantially dry mass of finely divided uranium dioxide particles at a velocity sufficient to maintain at least a major portion of the particles in fluid suspension and under conditions to convert the uranium dioxide particles to uranium tetrafluoride particles, withdrawing the uranium tetrafluoride particles from the reaction zone, contacting said particles with a gas containing fluorine under conditions to form uranium hexafluoride in the vapor state, and subsequently condensing the uranium hexafluoride.

9. The process recited in claim 8 wherein residual hydrogen fluoride gas is purged from the uranium tetrafluoride particles prior to contact with the gas containing fluorine.

10. A process of preparing a uranium fluoride which comprises passing hydrogen gas into a reaction zone containing a substantially dry mass of finely divided uranosic oxide particles at a velocity sufficient to maintain at least a major portion of the particles in fluid suspension and under conditions to convert the uranosic oxide particles to uranium dioxide particles, thereafter passing hydrogen fluoride into the reaction zone at a velocity sufficient to maintain at least a major portion of the particles of uranium dioxide in fluid suspension and under conditions to convert the uranium dioxide particles to uranium tetrafluoride particles, withdrawing the uranium tetrafluoride particles from the reaction zone, contacting said particles with a gas containing fluorine under conditions to form uranium hexafluoride in the vapor state, and subsequently condensing the uranium hexafluoride.

11. The process recited in claim 10 wherein the hydrogen fluoride-uranium dioxide reaction is elfected at a temperature between about 400 C. and 900 C;

12. A process of preparing a uranium halide from an oxide of uranium higher than the dioxide which comprises passing a fluidized mixture of a gas and substantially dry, finely divided particles of the higher oxide of uranium to a reaction zone, passing hydrogen and a hydrogen halide in the gaseous state into the base of said reaction zone at a velocity suflicient to maintain a major portion of the particles in fluid suspension and under conditions to convert the higher uranium oxide to uranium dioxide and then to the uranium halide, and thereafter withdrawing said uranuim halide from the reaction zone as a fluidized mixture with a gas.

13. The process recited in claim 12 wherein the hydrogen and hydrogen halide are successively passed into the base of the reaction zone.

14. The process recited in claim 12 wherein the hydrogen and hydrogen halide are simultaneously passed into the base of the reaction zone.

15. A continuous process of preparing uranium tetrafluoride which comprises passing a fluidized mixture of a gas and substantially dry, finely divided particles of uranosic oxide to a first reaction zone, passing a gas containing hydrogen into the base of said first reaction zone at a velocity sufficient to maintain a major portion of the particles in fluid suspension and under conditions to convert the uranosic oxide to uranium dioxide, continuously withdrawing a portion of the uranium dioxide particles from the base of said first reaction zone as a fluidized mixture with a gas, passing the last-mentioned fluidized mixture into a second reaction zone, passing a gas containing hydrogen fluoride into the base of said second reaction zone at a velocity sufficient to maintain a major portion of the particles in fluid suspension and under conditions to convert the uranium dioxide to uranium tetrafluoride, and continuously withdrawing uranium tetrafluoride particles from the base of said second reaction zone as a fluidized mixture with a gas.

16. A continuous process of preparing uranium hexafluoride which comprisespassing a fluidized mixture of a gas and substantially dry, finely divided particles of uranosic oxide to a first reaction zone, passing a gas containing hydrogen into the base of said first reaction zone at a velocity sufiicient to maintain a major portion of the 8 particles in fluid suspension and under conditions to convert the uranosic oxide to uranium dioxide, continuously withdrawing a portion of the uranium dioxide particles 'from the base of said first reaction zone as a fluidized mixture with a gas, passing the last-mentioned fluidized mixture into a second reaction zone, passing a gas containing hydrogen fluoride into the base of said second reaction zone at a velocity sufficient to maintain a major portion of the particles in fluid suspension and under conditions to convert the uranium dioxide to uranium tetrafluoride, continuously Withdrawing uranium tetrafluoride particles from the base of said second reaction zone as a fluidized mixture with a gas, admixing the lastmentioned mixture with fluorine gas under conditions to form uranium hexafluoride in the vapor state, and thereafter separately condensing the uranium hexafluoride.

17. The process. recited in claim 16 wherein excess hydrogen fluoride is purged from the uranium tetrafluoride prior to the fluorine gas-uranium tetrafluoride reaction.

18. A continuous process of preparing uranium hexafluoride which comprises passing a fluidized mixture of. a gas and substantially dry, finely divided particles of uranosic oxide to a first reaction zone maintained at a temperature bet-ween about 400 C. and 900 C., passing a gas containing hydrogen into the base of said first reaction zone at a velocity suflicient to maintain a major portion of the particles in fluid suspension whereby to Convert the .uranosic oxide to uranium dioxide, continuously withdrawinga portion of the uranium dioxide particles from the base of said first reaction zone as a fluidized mixture with a gas, passing the last-mentioned fluidized mixture into a second reaction zone maintained at a temperature between about 400 C. and 700 C., passing a gas containing hydrogen fluoride into the base of said second reaction zone at a velocity sufficient to maintain a major portion of the particles in fluid suspension whereby to convert the uranium dioxide to uranium tetrafluoride, continuously withdrawing hot uranium tetrafluoride from the base of said second reaction zone as a fluidized mixture With a gas, reacting the hot fluidized uranium tetrafluoride with fluorine gas at a temperature between about 200 C. and 400 C. to form uranium hexafluoride in the vapor state, and thereafter separately condensing the uranium hexafluoride.

References Cited in the file of this patent UNITED STATES PATENTS 1,299,560 Doerner Apr. 8, 1919 1,329,380 Doerner Feb. 3, 1920 1,355,105 Canon Oct. 5, 1920 1,434,486 DAdrian Nov. 7, 1922 1,810,053 Muller June 16, 1931 1,810,055 Muller June 16, 1931 1,814,392 Low July 14, 1931 1,877,961 Pokorny Sept. 20, 1932 1,984,380 Odell Dec. 18, 1934 1,988,541 Christensen Jan. 22, 1935 2,226,578 Payne Dec. 31, 1940 2,248,196 Plummer July 8, 1941 2,270,502 Bucher Jan. 20, 1942 2,309,034 Barr Jan. 19, 1943 2,311,564 Munday Feb. 16, 1943 2,325,516 Holt July 27, 1943 2,341,193 Scheineman Feb. 2, 1944 FOREIGN PATENTS 176,428 Great Britain Feb. 28, 1922 658,254 Germany Mar. 25, 1938 OTHER REFERENCES Mellcr: Comprehensive Treatise on Inorganic and Theoretical Chenm, vol. XII, pp. 74, 75, 80.

Mellor: Treatise on Inorganic Chemistry, vol. XII, p. 40. 

1. IN A PROCESS FOR PRODUCING A URANIUM TETRAHALIDE FROM AN OXIDE OF URANIUM, THE STEP OF PASSING A GAS CONTAINING A HYDROGEN HALIDE INTO A SUBSTANTIALLY DRY MASS OF FINELY DIVIDED URANIUM DIOXIDE PARTICLES AT A VELOCITY SUFFICIENT TO MAINTAIN A MAJOR PORTION OF THE PARTICLES IN FLUID SUSPENSION AND UNDER CONDITIONS TO CONVERT THE URANIUM DIOXIDE TO THE URANIUM TETRAHALIDE. 